The work presents and describes various mechanisms for the formation of a conductive channel in bipolar memristors of the vacancy and ionic types: in the first case, due to the generation and growth of conductive threads, and in the second, due to segregation processes with the formation of spatial associations of ions from the material of the active electrode. The current—voltage characteristics for both types of memristors are presented and a comparison of the design features of these memristors is conducted.

In an Ag/SnSe/Ge 2 Se 3 /W ionic type memristor, the activation energy of two main processes responsible for its operation has been determined, namely: the activation energy for the formation of a conductive channel and the activation energy for memristor degradation. By measuring the current-voltage characteristics, the electrical conductivity of the memristor in low- and high-resistance operating modes was assessed. To determine the activation energy, the Arrhenius law and the provisions of the thermodynamics of irreversible processes were used, in particular the second postulate of Onsager, according to which the growth rate of the irreversible part of the entropy of a system tending to equilibrium is proportional to the sum of the products of the flows occurring in the system and the generalized thermodynamic force corresponding to each flow. The equilibrium state of the memristor was taken to be the state in which the memristor lost the ability to function as a resistive memory cell. The flow of Ag+ ions – electromigration was used as a substance flow. For the first process, the activation energy was 0.24 eV, and for the second, 1.16 eV. The different values of activation energy reflect the difference between the agglomeration mechanism of formation of a current-conducting channel, typical of an Ag/SnSe/Ge 2 Se 3 /W memristor, and the “standard” mechanism of substance transfer based on a group of point defects, which accompanies the process of memristor degradation.

Experimental data on measurement of the resistance and electrical conductivity in the low-resistance mode of operation of a germanium-selenide-based memristor with a self-forming conductive channel in the form of a silver filament are obtained in the range of operating frequencies and temperatures. In the frequency experiment, the influence of the switching frequency is tested at room temperature in the range of 1–10 000 Hz. The main result of the experiment is the identification of a linear relationship between the electrical conductivity and the memristor operating cycle time in semilogarithmic coordinates, which made it possible to introduce a temperature-dependent kinetic constant. This experimental fact made it possible to establish the main parameter affecting the shape of the current–voltage characteristics, namely the thickness of the conductive channel.

The effect of temperature on degradation processes in an Ag/SnSe/Ge2Se3/W ionic memristor with a self-forming conductive channel in the temperature range of 22-65oC at a switching frequency of 100 Hz was studied based on determining the electrical conductivity of the memristor in low-resistance and high-resistance modes of operation. It has been established that at elevated temperatures, degradation processes occur faster and affect both the low-resistance and high-resistance modes of operation of the memristor. The degradation activation energy was determined to be 1.16 eV. Keywords: electrical conductivity, solid electrolyte, degradation, conductive channel.

The experimental data on the measurement of resistance and electrical conductivity in a low-resistance mode of operation of a memristor based on germanium selenide with a self-directed conductive channel in the range of switching frequencies and temperatures are presented. In the frequency experiment, the switching frequency effect is conducted at room temperature in the range of 1 to 10 000 Hz. An experiment to study the effect of temperature on resistance and electrical conductivity is carried out in the temperature range –10–65°C at a switching frequency of 10 Hz. The aim of this study is to determine the activation energy of the formation of a conductive channel. It is shown that in the temperature range 22–65°C electrical conductivity obeys the Arrhenius law with an activation energy of 0.19 eV; at temperatures below room temperature, the electrical conductivity is insensitive to temperature changes. The reasons for the low value of the activation energy are discussed.

It is shown based on the structural analysis by reciprocal space mapping and the experimental secondary ion mass spectrometry and transmission electron microscopy data that, along with lateral compressive stress, vertical compressive stress is induced in a multilayer epitaxial heterostructure with a metamorphic step-graded buffer. The reason for this stress is that interphase boundaries hinder complete stress removal at strain relaxation. The analysis carried out within the linear elasticity theory showed that the elastically strained state of the heterostructure layers is similar to the state arising during a two-stage deformation process (bulk and biaxial compression). It is shown that the free energy of the system in the metastable state is minimal in this case.

AbstractOn the basis of data on X -ray structural analysis performed by the method of reciprocal-space mapping and investigations using secondary-ion mass spectrometry and transmission electron microscopy, it is shown that vertical compressive stresses also arise in a multilayer epitaxial heterostructure comprised of a step-graded metamorphic buffer along with lateral compressive stresses. The cause of the appearance of vertical stresses is the effect of interlayer hardening, which arises due to the deceleration of fragments of glide dislocations by interphase boundaries. Analysis performed within the framework of the linear theory of elasticity shows that the elastically stressed state of the buffer steps is similar to the state that can be achieved as a result of a two-stage deformation process: bulk and biaxial compression. Bulk compression leads to large energy expenditures in the formation of the structure of the buffer steps, which is reflected, in particular, in violation of the coherence between the dislocation-free and the underlying layers.

On the basis of data on X-ray structural analysis performed by the method of reciprocal-space mapping and investigations using secondary-ion mass spectrometry and transmission electron microscopy, it is shown that vertical compressive stresses also arise in a multilayer epitaxial heterostructure comprised of a step-graded metamorphic buffer along with lateral compressive stresses. The cause of the appearance of vertical stresses is the effect of interlayer hardening, which arises due to the deceleration of fragments of glide dislocations by interphase boundaries. Analysis performed within the framework of the linear theory of elasticity shows that the elastically stressed state of the buffer steps is similar to the state that can be achieved as a result of a two-stage deformation process: bulk and biaxial compression. Bulk compression leads to large energy expenditures in the formation of the structure of the buffer steps, which is reflected, in particular, in violation of the coherence between the dislocation-free and the underlying layers.

ПРОЕКТИРОВАНИЕ МЕТАМОРФНОГО СТУПЕНЧАТОГО БУФЕРА, ОСНОВАННОЕ НА ФЕНОМЕНОЛОГИЧЕСКОМ ОПИСАНИИ СТРУКТУРНОЙ РЕЛАКСАЦИИ В ЭПИТАКСИАЛЬНЫХ СЛОЯХ А.Н.Алёшин, О

This paper presents a modified nonlinear model of the Fujii transistor that incorporates the gate capacitance values obtained by capacitance-voltage measurements. It is shown that the proposed model allows us to correctly determine the operating frequency of the transistor, taking into account the effect of charged dislocation lines in the barrier layer of the heterostructure. The operating frequency values obtained with this modified model are in good agreement with the measured values.

Приведены результаты исследований электрических и тепловых свойств фотопроводящих антенн для генерации терагерцового излучения на основе выращенного в низкотемпературном режиме GaAs (low-temperature grown GaAs, LT-GaAs) и InxGa1-xAs c повышенным содержанием индия (x>0.3). Показано, что мощность джоулева разогрева PH за счет влияния темнового тока в InxGa1-xAs в 3-5 раз превосходит аналогичную величину для LT-GaAs. Это обусловлено большой собственной проводимостью InxGa1-xAs при x>0.38. Была разработана и изготовлена теплоотводящая оснастка для фотопроводящей антенны. Результаты численного моделирования показали, что использование теплоотвода позволяет уменьшить рабочую температуру антенны на 16% для антенны на основе LT-GaAs на 40% для антенны на основе In0.38Ga0.62As и на 64% для антенны на основе In0.53Ga0.47As. DOI: 10.21883/FTP.2017.09.44893.8508

Spatial distribution of residual elastic strain in the layers of two step-graded metamophic buffers of various designs, grown by molecular beam epitaxy from ternary InxAl1–xAs solutions on GaAs(001) substrates, is obtained using reciprocal space mapping by three-axis X-ray diffractometry and the linear theory of elasticity. The difference in the design of the buffers enabled the formation of a dislocation-free layer with different thickness in each of the heterostructures, which was the main basis of this study. It is shown that, in spite of the different design of graded metamorphic buffers, the nature of strain fields in them is the same, and the residual elastic strains in the final elements of both buffers adjusted for the effect of work hardening subject to the same phenomenological law, which describes the strain relief process in single-layer heterostructures.

The research results of the resistance of signal converters with the operating frequency of 57–64 GHz, manufactured at the Institute of Ultrahigh Frequency Semiconductor Electronics on AlGaN/GaN/Al2O3 heterostructures to the action of special factors such as neutron and gamma radiation are presented. The results of evaluation of the long-term stability of the signal converters at high temperature are also discussed. The possible physical mechanisms of the changing characteristics are considered.

Методом построения карт обратного пространства, полученных с помощью трехосевой рентгеновской дифрактометрии, и на основе линейной теории упругости получены пространственные распределения остаточных упругих деформаций в слоях двух метамофных ступенчатых буферов различного дизайна, выращенных методом молекулярно-лучевой эпитаксии на основе тройных растворов InxAl1-xAs на подложках (001) GaAs. Разница в дизайне буферов обеспечивала образование в каждой из гетероструктур бездислокационного слоя с различной толщиной, что явилось основным базисом данного исследования. Показано, что, несмотря на различный дизайн метаморфных ступенчатых буферов, характер деформационных полей в них один и тот же, а остаточные упругие деформации в финальных элементах обоих буферов с учетом поправки на эффект деформационного упрочнения подчиняются тому же феноменологическому закону, который описывает процесс структурной релаксации в однослойных гетероструктурах. Работа выполнена при частичной финансовой поддержке РФФИ (гранты N 16-07-00187 А и 16-29-03033 офи\_м). DOI: 10.21883/FTT.2017.10.44965.068